phrase = "Don't panic"
plist = list(phrase)
print(plist)
#删除后四个字符
for i in range(4):
    plist.pop()
print(plist)
# 删除字符D
plist.pop(0)
#在上面已经删除D的基础上，后面接着删除'
plist.pop(2)
print(plist)
#extend添加
plist.extend([plist.pop(),plist.pop()])
print(plist)
#insert
plist.insert(2,plist.pop())
print(plist)
plist.insert(4,'o')
new_phrase = ''.join(plist)
print(new_phrase)
#Don't panic转换成on top
